#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/select.h>


#define BUF_SIZE 100

void error_handling(char *buf);


int main(int argc, char *argv[]){

	int serv_sock,clnt_sock;
	struct sockaddr_in serv_adr,clnt_adr;
	struct timeval timeout;
	fd_set reads, cpy_reads;

	socklen_t adr_sz;
	int fd_max, str_len, fd_num,i;
	char buf[BUF_SIZE];
	if (argc!=2)
	{
		printf("usage error\n");
		exit(1);
	}
	serv_sock=socket(PF_INET,SOCK_STREAM,0);
	memset(&serv_adr, 0,sizeof(serv_adr));
	serv_adr.sin_family=AF_INET;
	serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
	serv_adr.sin_port=htons(atoi(argv[1]));

	if(bind(serv_sock,(struct sockaddr*)&serv_adr, sizeof(serv_adr))==-1)
		error_handling("bind error");

	if (listen(serv_sock,5)==-1)
	{
		error_handling("listen error");
	}

	FD_ZERO(&reads);
	FD_SET(serv_sock, &reads);
	fd_max =serv_sock;

	while (1)
	{
			cpy_reads=reads;
			timeout.tv_sec=5;
			timeout.tv_usec=5000;
			if ((fd_num=select(fd_max+1, &cpy_reads, 0, 0,&timeout))==-1)
			{
				break;
			}
			if (fd_num==0)
			{
				continue;
			}

			for (i=0; i<fd_max+1 ;i++ )
			{
				if (FD_ISSET(i, &cpy_reads))
				{
					if (i == serv_sock)
					{
						adr_sz = sizeof(clnt_adr);
						clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr, &adr_sz);
						FD_SET(clnt_sock, &reads);
						if (fd_max< clnt_sock)
						{
							fd_max = clnt_sock;
						}
						printf("connected client: %d\n", clnt_sock);
					}
					else{
						str_len = read(i,buf,BUF_SIZE);
						if (str_len==0)
						{
							FD_CLR(i,&reads);
							close(i);
							printf("close client: %d \n", i);
						}else{
							write(i,buf,str_len);
						}
					}
				}
			}
	}
	close(serv_sock);
	return 0;

}

void error_handling(char* buf){
	fputs(buf, stderr);
	fputs('\n', stderr);
	exit(1);
}